Blackley played for the Single-A San Bernardino Stampede in 2002. He had
a 5-9 record with a 3.49 ERA in 21 games, 20 of which were starts.
He had 152 strikeouts in 121.1 innings, his strikeouts were second
among all Mariners minor leaguers.

Blackley played for the Double-A San Antonio Missions in 2003. His
2003 season was his most impressive of his minor league career. He
led the Texas
League with 17 wins; was second in ERA (2.61), fourth in
strikeouts (144) and fourth in innings pitched (162.1). His 17 wins
were the most by a Texas League pitcher since Jeff Reardon of the Jackson Mets in 1978.

He participated in the Texas League Postseason All-Star game and
was named to the World squad in the 2003 All-Star Futures Game at U.S.
Cellular Field on July 15. Blackley was also named the Mariners
minor league pitcher of the year by the organization.

In 2004, Blackley was named by Baseball
America as the #63 prospect out of 100 prospects. He was
named the third best prospect in the Mariners system, behind
pitchers Félix Hernández and Clint Nageotte,
and was their top left-handed prospect. Blackley began the
season in Triple-A with the Tacoma Rainiers. The Mariners, after
trading Freddy Garcia to the Chicago White
Sox, needed another starter and Blackley's contract was
purchased on July 1, 2004. He made his major league debut on that
same day against the Texas Rangers and allowed 4
runs on 6 hits in 5 2/3 innings and got the win. He became just the
sixth pitcher in Mariners history to start and win on their major
league debut.

After spending a month with the major league club in which he
went 1-3 with a 10.04 ERA in 6 starts, Blackley was optioned back
to Triple-A Tacoma on August 1, 2004. He had an 8-6 record with a
3.83 ERA in 19 games (18 starts) with Tacoma in 2004 before ending
the season on the disabled list with shoulder tendinitis in his
left arm.

Blackley missed the whole 2005 season while recovering from left
shoulder surgery.

Blackley spent the majority of the 2006 season with Double-A San
Antonio. After going 8-11 with a 4.06 ERA in 25 starts in Double-A,
Blackley was promoted to Triple A Tacoma at the end of August. He
made 2 starts in Tacoma and had a 1-1 record with a 4.09 ERA.

San
Francisco Giants

On April 1, 2007, following the end of Spring Training, he was traded to the San
Francisco Giants for outfielderJason Ellison. Blackley was immediately
optioned to Triple-A Fresno. Blackley played the whole
minor league season with the Grizzlies. He went 10-8 with a 4.66
ERA in 28 starts. He was recalled on September 21, and on September
23 made his first major league start since July 31, 2004 against
the Cincinnati
Reds. Blackley won his debut, giving up two runs in the first
inning and three hits in five innings. He walked four and struck
out five.

Philadelphia Phillies

After being outrighted off the San Francisco roster, on December
6, 2007, Blackley was selected by the Philadelphia Phillies in the
major league portion of the Rule 5 draft.

Towards the end of the 2008 spring training, Blackley was
placed on waivers. The Giants did not reclaim him and the Phillies
outrighted him to Triple-A Lehigh Valley. He became a free
agent after the season ended.

Arizona
Diamondbacks

On December 19, 2008, Blackley signed
a major league contract with the Arizona Diamondbacks.[1] On
April 1, 2009, Blackley was sent outright to Reno.[2]